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The nitrogen costs of photosynthesis in a diatom under current and future pCO2 (2015)

Li, Gang ; Brown, Christopher M ; Jeans, Jennifer A ; [et al.]

PANGAEA

In: Supplement to: Li, Gang; Brown, Christopher M; Jeans, Jennifer A; Donaher, Natalie A; McCarthy, Avery; Campbell, Douglas A (2015): The nitrogen costs of photosynthesis in a diatom under current and future pCO2. New Phytologist, 205(2), 533-543, https://doi.org/10.1111/nph.13037

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Publication Date: 2024-03-15

Description: With each cellular generation, oxygenic photoautotrophs must accumulate abundant protein complexes that mediate light capture, photosynthetic electron transport and carbon fixation. In addition to this net synthesis, oxygenic photoautotrophs must counter the light-dependent photoinactivation of Photosystem II (PSII), using metabolically expensive proteolysis, disassembly, resynthesis and re-assembly of protein subunits. We used growth rates, elemental analyses and protein quantitations to estimate the nitrogen (N) metabolism costs to both accumulate the photosynthetic system and to maintain PSII function in the diatom Thalassiosira pseudonana, growing at two pCO2 levels across a range of light levels. The photosynthetic system contains c. 15-25% of total cellular N. Under low growth light, N (re)cycling through PSII repair is only c. 1% of the cellular N assimilation rate. As growth light increases to inhibitory levels, N metabolite cycling through PSII repair increases to c. 14% of the cellular N assimilation rate. Cells growing under the assumed future 750 ppmv pCO2 show higher growth rates under optimal light, coinciding with a lowered N metabolic cost to maintain photosynthesis, but then suffer greater photoinhibition of growth under excess light, coincident with rising costs to maintain photosynthesis. We predict this quantitative trait response to light will vary across taxa.

Keywords: Alkalinity, total; Aragonite saturation state; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Cell biovolume; Chlorophyll a per cell; Chlorophyll c per cell; Chromista; Cytochrome c1; Fucoxanthin chlorophyll protein per cell; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Identification; Irradiance; Laboratory experiment; Laboratory strains; Light; Nitrogen content per cell; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Phosphate; Photosynthetic protein, PsbC; Photosynthetic protein PsbA; Photosynthetic protein PsbD; Photosynthetic protein Rubisco; Phytoplankton; Potentiometric; Primary production/Photosynthesis; Protein per cell; Ratio; Salinity; Silicate; Single species; Species; Temperature, water; Thalassiosira pseudonana; Treatment

Type: Dataset

Format: text/tab-separated-values, 1536 data points

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Electronic Resource

Response of the cyanobacterium, Oscillatoria tenuis, to low iron environments: the effect on growth rate and evidence for siderophore production (1992)

Brown, Christopher M. ; Trick, Charles G.

Springer

Archives of microbiology 157 (1992), S. 349-354

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ISSN: 1432-072X

Keywords: Catechol ; Cyanobacteria ; Hydroxamate ; Oscillatoria ; Iron ; Siderophore

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Cyanobacteria vary in their ability to grow in media contaning low amounts of biologically available iron. Some strains, such as Oscillatoria tenuis, are well adapted to thrive in low-iron environments. We investigated the mechanism of iron scavenging in O. tenuis and found that this cyanobacterium has a siderophore-mediated iron transport system that differs significantly from the traditional hydroxamate-siderophore transport system reported from other cyanobacteria. Unlike other cyanobacteria, this strain produces two types of siderophores, a hydroxamate-type siderophore and a catechol-type siderophore. Production of these two siderophores is expressed at two different iron levels in the medium, suggesting two different iron regulated uptake systems. We compared the production of each siderophore with the growth rate of the culture and found that the production of the catechol siderophore enhances the growth rate of the cyanobacterium, whereas the cells maintain lower than maximal growth rates when only the hydroxamate-type siderophore is being produced.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00248680

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3

Electronic Resource

Decoupling Orientation Recovery from Position Recovery with 3D-2D Point Correspondences (1999)

Carceroni, Rodrigo L. ; Brown, Christopher M.

Springer

Journal of mathematical imaging and vision 11 (1999), S. 179-193

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ISSN: 1573-7683

Keywords: pose recovery ; extrinsic calibration ; visual navigation

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Abstract We propose a new algorithm for model-based extrinsic camera calibration that allows one to separate the recovery of the relative orientation of the camera from the recovery of its relative position, given a set of at least three correspondences between model and image points. The key idea is to replace each (real) model point whose correspondence is known by two (virtual) model edges, and then to use the fact that these edges have pairwise intersections in 3D space to derive a set of alignment constraints. We provide a proof that the resulting technique is essentially more powerful than any of the traditional methods for decoupled orientation and position recovery based uniquely on line correspondences. We also present a detailed example of a real-life application that benefits from our work, namely autonomous navigation using distant visual landmarks. We use simulation to show that, for this specific application, our algorithm, when compared to similar techniques, is either significantly more accurate at the same computational cost, or significantly faster with roughly the same average-case accuracy.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008347631264

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4

Electronic Resource

The theory and practice of Bayesian image labeling (1990)

Chou, Paul B. ; Brown, Christopher M.

Springer

International journal of computer vision 4 (1990), S. 185-210

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ISSN: 1573-1405

Source: Springer Online Journal Archives 1860-2000

Topics: Computer Science

Notes: Abstract Image analysis that produces an image-like array of symbolic or numerical elements (such as edge finding or depth map reconstruction) can be formulated as a labeling problem in which each element is to be assigned a label from a discrete or continuous label set. This formulation lends itself to algorithms, based on Bayesian probability theory, that support the combination of disparate sources of information, including prior knowledge. In the approach described here, local visual observations for each entity to be labeled (e.g., edge sites, pixels, elements in a depth array) yield label likelihoods. Likelihoods from several sources are combined consistently in abstraction-hierarchical label structures using a new, computationally simple procedure. The resulting label likelihoods are combined with a priori spatial knowledge encoded in a Markov random field (MRF). From the prior probabilities and the evidence-dependent combined likelihoods, the a posteriori distribution of the labelings is derived using Bayes' theorem. A new inference method, Highest Confidence First (HCF) estimation, is used to infer a unique labeling from the a posteriori distribution that is consistent with both prior knowledge and evidence. HCF compares favorably to previous techniques, all equivalent to some form of energy minimization or optimization, in finding a good MRF labeling. HCF is computationally efficient and predictable and produces better answers (lower energies) while exhibiting graceful degradation under noise and least commitment under inaccurate models. The technique generalizes to higher-level vision problems and other domains, and is demonstrated on problems of intensity edge detection and surface depth reconstruction.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00054995

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5

Electronic Resource

Control of selective perception using bayes nets and decision theory (1994)

Rimey, Raymond D. ; Brown, Christopher M.

Springer

International journal of computer vision 12 (1994), S. 173-207

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ISSN: 1573-1405

Source: Springer Online Journal Archives 1860-2000

Topics: Computer Science

Notes: Abstract A selective vision system sequentially collects evidence to answer a specific question with a desired level of confidence. Efficiency comes from processing the scene only where necessary, to the level of detail necessary, and with only the necessary operators. Knowledge representation and sequential decision making are central issues for selective vision, which takes advantage of prior knowledge of a domain's abstract and geometrical structure (e.g., “part-of” and “adjacent” relationships), and also uses information from a scene instance gathered during analysis. The TEA-1 selective vision system uses Bayes nets for representation, benefit-cost analysis for control of visual and nonvisual actions; and its data structures and decision-making algorithms provide a general, reusable framework. TEA-1 solves the T-world problem, an abstraction of a large set of scene domains and tasks. Some factors that affect the success of selective perception are analyzed by using TEA-1 to solve ensembles of randomly produced, simulated T-world problems. Experimental results with a real-world T-world problem, dinner table scenes, are also presented.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01421202

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6

Electronic Resource

Controlling eye movements with hidden Markov models (1991)

Rimey, Raymond D. ; Brown, Christopher M.

Springer

International journal of computer vision 7 (1991), S. 47-65

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ISSN: 1573-1405

Source: Springer Online Journal Archives 1860-2000

Topics: Computer Science

Notes: Abstract Advances in technology and in active vision research allow and encourage sequential visual information acquisition. Hidden Markov models (HMMs) can represent probabilistic sequences and probabilistic graph structures: here we explore their use in controlling the acquisition of visual information. We include a brief tutorial with two examples: (1) use input sequences to derive an aspect graph and (2) similarly derive a finite state machine for control of visual processing. The first main topic is the use of HMMs in both their learning and generative modes, and their augmentation to allow inputs sensed during generation to modify the generated outputs temporarily or permanently. We propose these augmented HMMs as a theory of adaptive skill acquisition and generation. The second main topic builds on the first: the augmented HMMs can be used for knowledge fusion. We give an example, the what-where-AHMM, which creates a hybrid skill from separate skills based on object location and object identity. Insofar as low-level skills can be learned from the output of high-level cognitive processes, AHMMs can provide a link between high-level and low-level vision.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00130489

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Effect of cell cycle arrest on intermediate metabolism in the marine diatomPhaeodactylum tricornutum (2017)

Kim, Joomi ; Brown, Christopher M. ; Kim, Min Kyung ; [et al.]

National Academy of Sciences

In: PNAS - Proceedings of the National Academy of Sciences of the United States of America. 2017; 114(38): E8007-E8016. Published 2017 Sep 05. doi: 10.1073/pnas.1711642114.

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Publication Date: 2017-09-05

Description: The inhibitor NU 2058 [6-(cyclohexylmethoxy)-9H-purin-2-amine] leads to G1-phase cell cycle arrest in the marine diatom,Phaeodactylum tricornutum,by binding to two cyclin-dependent kinases, CDKA1 and CDKA2. NU 2058 has no effect on photosynthetic attributes, such as Fv/Fm, chlorophylla/cell, levels of D2 PSII subunits, or RbcL; however, cell cycle arrest leads to unbalanced growth whereby photosynthetic products that can no longer be used for cell division are redirected toward carbohydrates and triacylglycerols (TAGs). Arrested cells up-regulate most genes involved in fatty acid synthesis, including acetyl-CoA carboxylase, and three out of five putative type II diglyceride acyltransferases (DGATs), the enzymes that catalyze TAG production. Correlation of transcriptomes in arrested cells with a flux balance model forP. tricornutumpredicts that reactions in the mitochondrion that supply glycerate may support TAG synthesis. Our results reveal that sources of intermediate metabolites and macromolecular sinks are tightly coupled to the cell cycle in a marine diatom, and that arresting cells in the G1 phase leads to remodeling of intermediate metabolism and unbalanced growth.

Print ISSN: 0027-8424

Electronic ISSN: 1091-6490

Topics: Biology , Medicine , Natural Sciences in General